netdev - Re: [PATCH bpf-next 1/2] selftests/bpf: skip verifier tests that depend on CONFIG_CGROUP

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Date:   Wed, 12 Dec 2018 10:59:13 -0800
From:   Stanislav Fomichev <sdf@...ichev.me>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org,
        davem@...emloft.net, ast@...nel.org, daniel@...earbox.net
Subject: Re: [PATCH bpf-next 1/2] selftests/bpf: skip verifier tests that
 depend on CONFIG_CGROUP_BPF

On 12/12, Alexei Starovoitov wrote:
> On Wed, Dec 12, 2018 at 10:27:24AM -0800, Stanislav Fomichev wrote:
> > The following prog types don't make sense without bpf cgroup:
> > * BPF_PROG_TYPE_CGROUP_SKB
> > * BPF_PROG_TYPE_CGROUP_SOCK
> > * BPF_PROG_TYPE_CGROUP_SOCK_ADDR
> > 
> > Skip running verifier tests that exercise these prog types if
> > kernel is built without proper support.
> > 
> > See commit e5c504858a18 ("selftests/bpf: skip verifier sockmap tests
> > on kernels without support") for original motivation.
> > 
> > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> > ---
> >  tools/testing/selftests/bpf/test_verifier.c | 35 +++++++++++++++++++++
> >  1 file changed, 35 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> > index f5015566ae1b..b5470a399996 100644
> > --- a/tools/testing/selftests/bpf/test_verifier.c
> > +++ b/tools/testing/selftests/bpf/test_verifier.c
> > @@ -44,6 +44,7 @@
> >  /* fallback to all features enabled */
> >  # define CONFIG_BPF_STREAM_PARSER 1
> >  # define CONFIG_XDP_SOCKETS 1
> > +# define CONFIG_CGROUP_BPF 1
> 
> I really don't like where these is going.
> I think previous set should be reverted.
> This is not a scalable approach.
> Use libbpf probing approach to check whether feature is present instead.
I can probably add runtime probing instead of depending on compile-time
config, but I think that we would still need some per-test mechanism
to say that it depends on feature X (per-test .config_disabled or
similar).
Will moving these checks to runtime address your concern? (there is sill a
scalability issue though)